1. Field of the Invention
The present invention relates to a vibrating actuator such as an ultrasonic motor.
2. Description of the Related Art
One vibrating actuator such as a conventional ultrasonic motor is disclosed in Japanese Utility Model Laid-Open No. 2-94488, for example, as shown in FIGS. 6-8. In a bar-type vibrating actuator, electric-energy-to-mechanical-energy converting elements (electro-mechanical energy conversion elements) such as piezoelectric elements (1a and 1b) and electrode plates for feeding power to the piezoelectric elements are arranged between a pair of elastic bodies (a front vibrator 3 and a rear vibrator 4), and the pair of elastic bodies are clamped with clamping members. The vibrating actuator comprises a vibration member in which the piezoelectric elements and the electrode plates are interposed between the pair of elastic members and a contact body (movable body 6) that is pressed into contact with one of the elastic bodies. The contact body is driven by either a combination of a vertical vibration motion along the longitudinal axis of the vibration member and a torsional vibration motion about the longitudinal axis or a composition of bending vibration motions of the vibration member having different phases.
A flexible printed circuit board (2) is used to feed an alternating current signal such as an alternating current voltage from a drive control circuit to the piezoelectric elements of the vibration member. Input terminals (2a-2c) connected to the electrode plates arranged in the vibration member are constructed of the flexible printed circuit board, and the flexible printed circuit board (2) is interposed between the elements of the vibration member. Lead portions of the flexible printed circuit board (2) are bent to run along the circumferential surfaces of the vibration member elements.
When the flexible printed circuit board is bent, a stress takes place at its bent portion. The vibration of the vibration member occasionally breaks the flexible printed circuit board at its bent portion.
If the curvature of the bent portion is increased to reduce the stress taking place at the bent portion, the overall diameter of the actuator including the flexible printed circuit board becomes larger.